a(n) = Sum_{k=1..n, gcd(n,k) = 1} k^3.

Terms

a(0) =1a(1) =1a(2) =9a(3) =28a(4) =100a(5) =126a(6) =441a(7) =496a(8) =1053a(9) =1100a(10) =3025a(11) =1800a(12) =6084a(13) =4410a(14) =7200a(15) =8128a(16) =18496a(17) =8910a(18) =29241a(19) =16400a(20) =29106a(21) =27830a(22) =64009a(23) =27936a(24) =77500a(25) =54756a(26) =88209a(27) =67032a(28) =164836a(29) =52200